Special HTTP headers for Trellis

Trellis/Cassandra offers some special HTTP request headers to enable customization of workflows and persistence. The most important is Cassandra-Chunk-Size, which, when applied to a request to persist binary data, will set the size of chunk (in bytes) that is used to chunk out the bitstream. This is particularly important if you expect to distribute computation across your Cassandra cluster. You will want to set this value high enough that a given distributed task will be able to complete on any resource to which it is applied without requiring data from more than one node.